Palisades, as discussed in last week’s installment, were an effective obstacle to place in front of works. There’s something about a wall of pointed fence posts that naturally prompts the attacker to consider alternative routes. But, being basically a wood fence, the palisade was vulnerable to artillery fire. A barrage of solid shot and shell could dismantle a palisading from a safe distance. Thus, as Mahan suggested, the best place for a palisade was on the counterscarp, thus keeping the obstacle under shelter from direct fire. Thus, in Mahan’s view, this obstacle was best employed in conjunction with the ditch. There were two additional manners in which Mahan felt a palisading could enhance the ditch, which he identified with separate names – fraise and stockade.
About the fraise, Mahan wrote:
Fraise. This obstacle is formed of palisades, placed in juxtaposition, either horizontally, or slightly inclined. The best position for a fraise is on the berm, or a little below it, so as to be covered by the counterscarp crest. The part of the fraise under the parapet is termed the tail, and is about five feet long. To make a fraise, a horizontal piece of four-inch scantling, termed a cushion, is first laid parallel to the berm; each palisade is nailed to this, and a thick riband is nailed on top of the fraise near the end.
Figure 24, provided by Mahan, illustrates a fraise placed on the berm of a fortification, slightly declined (which is the word I think Mahan intended to use) over the ditch:
As you can see, this makes a formidable obstacle for an adversary trying to claw out of the ditch. But there are some particulars the engineer had to mind when placing a fraise, lest it become less formidable:
The point of the fraise should be at least seven feet above the bottom of the ditch, and should not project beyond the foot of the scarp, so as not to shelter the enemy from logs, stones, &c., rolled from the parapet into the ditch.
Such arrangements ensured the enemy would have to do “overhead” work if the fraise were dismantled by hand; prevent him from simply climbing over the fraise and walking up the parapet; and gaining some lodgement under the fraise. We see the textbook example demonstrating all those requirements, particularly that a vertical line drawn from the foot of the scarp passes just beyond the point of the fraise. The attacker would have to find a foothold on the slope of the scarp … which should also be revetted and otherwise made difficult for footholds.
The disadvantages of the fraise was, of course, the need to plan in advance of erection of the parapet and the labor required.
Another variation on this theme was to place posts on the floor of the ditch in a manner to deny any footfall. In pre-war texts, Mahan called this a stockade:
Stockade. Trunks of small trees from nine to twelve inches in diameter, and twelve feet long, are selected to form a stockade. They are planted in juxtaposition, in a similar manner to a palisading, and are used for the same purposes.
A literal examination of this passage is the palisade used hewn posts while the stockade uses the whole, but smaller, tree. Of note, in the post-war manuals Mahan used the archaic “stoccade.” Though the significance of such is lost on me. Later into the post-war period, Junius Wheeler offered this illustration for the fraise:
More elaborate than Mahan’s illustration, but matched to far less text. Wheeler’s version has an inclined fraise on the crest of the counterscarp, protected by a glacis. To clear that counterscrarp fraise, the attacker would stand elevated directly under the opposing flanks or faces… and thus be in a very “hot” zone. There is one fault we would note from Wheeler’s diagram – the points of the fraise extend well beyond the foot of the scarp and counterscarp, as the case may be. This is mitigated somewhat by the obstacles on the floor of the ditch. Those are what Mahan called small pickets, and would have incorporated entanglements. That, however, is a subject we’ll discuss in detail later. Just be mindful those pickets served to reduce the attacker’s mobility within the ditch, augmenting the other obstacles.
Closing the discussion of stockades, Mahan offered this passage:
The manner of arranging a stockade, which is sometimes termed a picket, as a primary defense, will be described in another chapter.
Readers should sense two irritants in that sentence. So… a stockade is placed like a palisade but is a picket? But, as mentioned in relation to Wheeler’s diagram, small pickets are described as something clearly not related, in arrangement, to a palisade. Imagine the student trying to fix in their mind what word should be used for precision.
Secondly, Mahan alludes to use of a stockade in a manner completely removed from the employment mentioned for palisades. Certainly, the short description brings to mind the old frontier fortifications – stockade forts. Wheeler offered this illustration for a stockade employed as a primary means of defense:
At once, this is a recognizable defensive feature… to anyone having watched a western movie or two. And this is a form of defense which is best discussed in detail later. But clearly it is not a palisade. Thus we have another term which we need to weigh out when using … or more importantly when we see it used.
Circling back to the point – the point of the fraise that is – with this variation in employment of the palisade, we see, given ample time and resources, the defender could mitigate many of the flaws inherent within a profile. In particular, the ditch could become a very difficult area to reach and move beyond.
(Citation from Dennis Hart Mahan, A Treatise on Field Fortifications, New York: John Wiley, 1852, page 46-7.)